Speech recognition technology faces the challenge that every person has an essentially unique voice; an individual's set of voice characteristics are sometimes referred to as their “speech profile.” Existing speech-recognition systems have addressed the multitude of speech profiles in different ways. Some systems have several adjustable “acoustic models” and select and adjust one of them for each user. An acoustic model is a statistical representation of the occurrence of phonemes, diphones, triphones, etc. By using an acoustic model that fits the user's speech profile, the system can better recognize the user's speech. Other systems use only one acoustic model for all users. Such systems can only recognize a limited set of commands.
The systems with adjustable acoustic models go through a setup procedure to select and adjust an acoustic model so that it best fits the user's speech profile. Initially, the user may select a suitable one among a few acoustic models; for example, two acoustic models may be labeled “American English” and “British English,” respectively. In a typical setup procedure, the system adjusts the selected acoustic model by having the user read numerous predetermined text sequences into a microphone. By adjusting the acoustic model while comparing the user's voice with the known contents of the text sequence, the system identifies an adjustment configuration of the acoustic model that best fits the user's speech profile.
One problem with these systems is that it is inconvenient for the user to read the text sequences. Another problem is that it takes time to make the system operable due to the setup procedure. The lengthy setup procedure, in turn, makes it more difficult to continue using the speech-recognition system if the user's voice changes, for example due to illness. These problems also render the existing speech-recognition systems with adjustable acoustic models impractical in applications such as telephony or online services, which cannot accommodate an extensive procedure for setting up the system.
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